Stencil printing apparatus



J. B- THOMAS STENCIL PRINTING APPARATUS March 5, 1957 Filed April 19, 1951 5 Sheets-Sheet 1 IN VEN TOR.

JOHN B; THOMAS BY y iff a;

ATTORNEY March 5, 1957 J. B. THOMAS STENCIL PRINTING APPARATUS 5 Sheets-Sheet 2 Filed April 19. 1951 IN V EN TOR.

JOHN B. THOMAS ATTORNEY March 5, 1957 J. B. THOMAS 2,733,709

STENCIL PRINTING APPARATUS Filed April 19, 1951 5 Sheets-Sheet 3 IN V EN TOR.

JOHN B. THOMAS ATTORNEY March 5, 1957 J. B. THOMAS 9 STENCIL PRINTING APPARATUS Filed April 19. 1951 5 Sheets-Sheet 4 INVENTOR. 1: .1 El JOHN B.THOMA3 ATTORNEY March 5, 1957 J. B. THOMAS 2,783,709

STENCIL PRINTING APPARATUS Filed April 19. 1951 5 Sheets-Sheet 5 INVEN TOR.

JOHN B. THOMAS ATTORNEY United States Patent" STENCIL PRINTING APPARATUS John B. Thomas, Watertown, Conn., assignor, by mesne assignments, to Princeton Knitting Miiis, lncx, Watch town, Conm, a corporation of Connecticut Application April 19, 1951, Serial No. 221,793

6 Claims. (Cl. 101-123) This invention relates to an apparatus for printing sheets such as textile fabric webs, plastic films and paper with the aid of a stencil. For simplicity, such apparatus will be referred to hereinafter simply as a silk screen printing machine, it being understood that this term merely is a trade designation for a stencil printing machine and does not indicate that the stencil necessarily is of silk. More particularly, the invention pertains to a scraper for use in a machine of the character described.

It is an object of the invention to provide a two-blade scraper having a rapid-acting and efiicient mechanism for raising one blade and lowering the other at opposite ends of the scraper stroke whereby to prevent the scraper from occasionally depositing drops of tears of ink from its rear face as it traverses the screen.

It is another object of the invention to provide a mechanism which can be set up rapidly and at will as either a two-blade scraper or a single-blade scraper.

It is another object of the invention to provide a scraper of the floating type, i. e., one mounted to permit the scraper weight to rest on the operative edge of the blade, wherein a counteracting force, preferably adjustable in nature, is adapted to relieve the stencil screen of part of the weight of the scraper.

In the latter connection, it is a more specific object of the invention to provide a floating scraper of the character described wherein a simple and easily adjustable arrangement is included to vary the counter-acting force.

It is another object of the invention to provide a scraper of the character described which comprises comparatively few and simple parts and is of a durable construction.

It is another object of the invention to provide a scraper of the character described whose action is rapid enough to permit the same to be used as part of a power-driven silk screen machine.

Other objects of the invention will in part be obvious and in part will be pointed out hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangements of parts which will be exemplified in the machine hereinafter described and of which the scope of application will be indicated in the appended claims.

In the accompanying drawings, in which is shown one of the various possible embodiments of this invention,

Fig. 1 is a fragmentary plan view of a front corner of a silk screen printing machine constructed in accordance with the present invention, the scraper being shown approaching the front of the machine;

Figs. 2 and 3 are enlarged sectional views taken substantially along the lines 2-2 and 3-3, respectively, of Fig. 1;

Fig. 4 is a sectional view taken substantially along the line 4-4 of Fig. 3;

Fig. 5 is a view similar to Fig. 3, but at a later stage of operation, to wit the midpoint of reversal;

Fig. 6 is a view similar to Fig. 5, but at a still later stage, to wit shortly after reversal;

Fig. 7 is a view similar to Fig. 2 but at a stage of operation corresponding to big. 0;

mg. as is an enlarged sectional view taken substantially along the line 15-h of mg. 1;

mg. 9 IS the sectional view taken substantially along the hue 99 of mg. 8;

rug. 10 is a view similar to Fig. 2, but showing a scraper W11. a single, rather than a dOuDlC, blade; and

mg. 11 18 a view similar to rig. H) but with the scraper at the midpoint of reversal.

keterrlng now in detail to the drawings, the reference numeral 20 denotes a silk screen printing machine embodying the invention and including a conventional prlnting table 22. At the opposite sides of the tame, Irontto-oack rails R are provided which are or suitable construenon and are supported from the table in a suitable manner. '1 yp1cal constructions and supports tor the rails are shown in the co-pendmg application of John B. Thomas and Courtney 11;. Moornouse, Serial No. 720,504, for Stencil Printing Apparatus, med reoruary 5, 1347, now Patent No. 2,031,366, and 111 co-pendlng application, Serial No. 221,794, tiled simultaneously WlIlJ the present application, for Stencil .llllllllllg Apparatus, now Patent No. 2,637,269 both said applications being assigned to the assignee of the present application.

"the rails shown herein constitute a pair of hollow tubular tracks 24, 26 at each side of the machine, said tracks being parallel to one another and horizontal when the machine is prmhng. The two tracks of each pair are secured to one another at the front of the machine by a housing 28 in which there is located a sprocket (not shown) about which a chain 3%) is trained. The upper flight 32 of the chain is disposed in the upper track 24, and the lower flight 34 in the lower track. A suitable mechanism, for instance sprockets (not shown), engages the chains at the rear ends of the tracks and is alternately power-driven in opposite directions, for example as shown in said applications.

The machine further includes a stencil screen 38 carried by a stencil frame 40, that is supported for movement toward the table for printing and away from the table after printing. In the normal use of the machine, a scraper S is moved to and fro across the screen pushing a pool of ink I in front of it. Said scraper is carried by a support whose ends are mounted for movement on the rails R, being power-driven by the chains 30.

The present invention is concerned with the construction of the scraper, the scraper support and the mount for the ends of the scraper support.

More specifically, the scraper support includes a draw bar 42 each of whose opposite ends is formed into a yoke 44. The yoke at each end of the bar isvertically pierced to receive a locking pin 46 (see Fig. 4). Said yoke is adapted to receive a flange 48 which is provided with an elongated opening to pass the locking pin 46. This arrangement enables the bar to be disengaged from the flanges simply by lifting the locking pins.

The flanges 48 on opposite sides of the machine are identical and are supported and moved in identical manner so that only one of such flanges and its mount has been shown and will be described in detail.

Said flange is carried by a truck 50 including a pair of wheels 52, 54 which ride on and between the tracks 24, 26 and are journalled for rotation about parallel horizontal axes on a vertical plate 56 so that the plate only is able to move axially on the rails R. This plate is secured to the upper flight of the chains by a bracket 57 (see Fig. 4) extending through a longitudinal slot in the bottom of the upper track 24.

A second vertical plate 58 is disposed in face-to-face contact with the inside surface of the outer plate 56. The

plate 58 carries two outwardly extending studs 60, 62 on which rollers 64 are journalled, these rollers being slidable in vertical slots 66, .58 in the plate 56 whereby the plate 58 is mounted for vertical movement with respect to plate 56. In order to holdthe plate 58 captive, the heads of the studs 6%,62 are enlarged to'exceed the width of the slots 66, 68. Vertical movement of the plate 58 is limited by abutmentofthc rollers against the ends of the slots 66, 63.

A third vertical plate 70 is disposed in face-to-i'ace' contact with the inside surface of the second plate 58. For convenience, the third plate"'-70 will be referred to asthe inner plate, the second plate 58 as 'theintermediate plate, and the first plate-56 as theou-te'r-plate.

The intermediate plate may have a peripheral-contour substantially the same as that of the outer plate (see Figs. 3 and S); however, the inner plate is considerably shorter than theintermediate plate and its .top edge lower in order to permit the-flange 43 to be supported-from-saidintermediate plate.

A horizontal stub shaft 72 is setin a bushing 74 that is forceditted in the intermediate plate, sa-id shaftextending inwardly a-direction perpendicular to the plates. Rotatable onthe bushing is a'collar -76 that-is held captive by ascrew '78 threaded in the collar with its tip rid-ingin anannular groove 88 in the shaft 7 2. Secured to the collar 76is an arm 82 at whose upper endthe flange 48 is mounted. Said flange extends across-the 89 in the inner plate so that said inner plate is constrained for horizontal movement with respect to the intermediate plate. To captively secure the inner plate to the intermediate plate, the heads of the studs 86, 88 are. enlarged to a size greater than the slots 89.

It thus will be appreciated that only relative horizontal movement can take place between theinner andintermediate plates, and only relative vertical .mouernent can take place between the intermediate andtouter plates.

The followers heretofore mentioned for engaging the cam sections of the inner plate. are located at? both ends of the both sets of rails R. inasmuch as. allsets-offollowers arethe same, only one such set is illustratedand described.

One follower Sills provided consisting. ofangoller-Z92 rotatable on a horizontal spindle 24 carried by .a clevis The second follower 106in=cludes a roller 108 rotatable on a-horizontal spindle 110 carried by a clevis 112 on the end of a rod 114 parallel to the rod 98. The roller is in horizontal alignment with the cam section a-b. Said rod is slidable in a bore in the bracket 100. A set screw 116 threaded in the bracket has its tip disposed to engage an elongated flat 118 running axially of the rod 114 so that the follower 106, can be adjusted with respect to the follower 90. These two followers should be so relatively setthat the follower 1 0;6 initiates .its action slightly in advance of that of the follower 90.

As a truck approaches one end .orthe .otherof the rails R in adirection, for example, indicated by the arrow A, the follower 106 first will engage the cam section ab on the. inner. plate. inasmuch as this section slopes downwardly away from the follower, when the inner plate encounters the follower, said plate will be lifted vertically. Since the inner and intermediate plates can experience no relative vertical movement, the intermediate plate also willbe'lifted, the latter being shift.- able vertically with respect to the outer plate. Lifting the intermediate plate raises the flange 4t and, hence,

.;the drawbar and scraper. The relative positions of the various plates and followers at the moment the follower 106 first contacts the inner plate is shown in Fig. 3.

Further movement of the truck in the direction A will cause the follower to engage the section cd. At first the spring will be compressed; but after a certain degree of compression is reached the roller 92 will not give-any further, and, upon subsequent movement of the truck toward said follower, the inner plate will beshifted horizontally with respect to the intermediate plate in a direction away from this follower.

forming one side of the block with an enlarged head 124 and'by mounting a plate 126 on the opposite side of the block, both the'enlarged head and plate sliding'on the inner and enter surfaces of the arm. Said block is urged in a direction away from the axis of oscillation of the arm by a helical'compression, spring 128.

96on therendof ahorizontal rod 98 whoselohgitudinal axis is parallel to the direction of movement of the truck 59. The-roller is in horizontal alignmentwith the cam section c d The rod is slidablein a bore in abracket lllt) adjustahlyclamped on the tracks 24, 26 andthe-far' end of the rod is threaded to receive a stop nut102 and a lock nut lll. Ahelical compression spring 105, encircles the rod and is heldunder compression between. the base of the clevis 96 and the bracket 18%). A. transverse-pin 101 sliding in a slot 103 in the rod prevents, therod from turning.

The: "block fixedly carries'a long outwardly extending spindle'lddwhich passes through :a central notch 1.32 (Fig.5) in the top edge'of the inner plate 70 and through a central notch-134 in the intermediate plate 58. These :tWQ notches are of .such configuration "that they will icotreme angular position shown in Fig. 6.

More specifically, the notch 132 has a bottom edge of V-shaped profile with its lower tip-rounded to'substantially the curvature of the spindle 130. The bottom edge of the notch 13A is of W-shaped'configuration .With its centfal; and its two lower tips rounded to the The follower as thus is positioned to engage thezcam curvature of the spindle;

When the truck is moving in any given direction, for I example in the direction A toward the front of the machine i'a s shownin Fig. 3, the arm 82 is inclined in this direction and the spindle 130 is situated in the lower tip ofthe. (:shaped notch .134 which is closest to theend of the machine being approached by the truck. At the me: t me- 1 s indl s se in theltower, p ofthe vv shaped notch 132 and the inner-plateleads the intermedimm of the cam q arer thy h fo lo rill:

raise the inner and intermediate plates but will not affect their relative horizontal position.

When the cam section c-d engages the follower 90 and the spring 105 has compressed, the inner plate will shift relative to the intermediate plate in a direction B (Fig. away from the direction of movement A'of the truck, causing the inclined edge of the V-shaped notch 132 nearer the engaged follower to urge the spindle 130 upwardly and toward the other lower tip of the W-shaped notch 134. This shifts the spindle upwardly toward the central hump of the W-shaped notch. As such movement occurs the block 122 will ride upwardly against the force of the spring 128, permitting the spindle to clear the hump and be biased by said spring intothe other lower tip of the W-shaped notch. .Due to this motion of the spindle, the arm 82 will shift to its opposite extreme angular position shown in Fig. 6. Upon movement of the scraper to the opposite end of the machine, the inner plate 70 will be shifted by a follower back to the position with respect to the intermediate plate shown in Fig. 3, so that the arm 82 will be oscillated to its first angular position.

Thus, upon reaching either end of the machine, the bar 42 first will be raised and immediately thereafter rotated through a small angle, in the illustrated machine about 30.

The bar 42 has secured thereto a pair of spaced hangers 136, only one of which is shown on the drawings. A hanger is located near each end of the bar, being adjustably secured thereto, as by a set screw 138 which engages a key set in the drawbar, so that its position can be varied to centralize the scraper S on the screen.

Each hanger 136 has rotatably mounted thereon, 'asby a pin 140, a blade clamp 142. The pins 140 of the two hangers are horizontally registered so that the blade clamps may oscillate in unison. Each clamp is provided with two slots 144, 146 which are arranged to converge upwardly, the longitudinal center lines of the slots if errtended intersecting at the longitudinal axis of the pins 140. Two scraper blades 148, 150 are included, these being of conventional shape and material. Each blade extends between the two clamps and has its ends secured in either the registered slots 144 or the registered slots 146. The rounded tips of both blades are equidistant from the longitudinal axis of the pins 140.

Each blade clamp has mounted on its upper edge an abutment lug 152 which oscillates with the clamp about the pin 14%. Extending inwardly from the hanger are two stop screws 154, 156 which lie in the path of travel of the abutment lug 152. Said screws have their shanks disposed eccentrically of their heads and are secured in any desired angular position by jam nuts (not shown) on the opposite side of the hanger. As illustrated in Figs. 2 and 7, the screws 154, 156 are disposed to lock the blade clamp against oscillation with the clamp so located that when the arm 82 is in one extreme angular position, the blade 150 is substantially perpendicular to the screen 38 (Fig. 2) and when the arm 82 is in its other extreme angular position the blade 148 is substantially perpendicular to the screen (Fig. 7).

It has been observed that by varying the angle between the scraper blade and screen, different printing effects can be secured, and it is for this reason that the heads of the screws 154, 156 are disposed eccentrically relative to their shanks, for, by turning the screws so as to increase the spacing between their heads and thereby to allow oscillation of the blade clamps, the angle between each scraper blade and the stencil screen can be reduced below 90. Such alternative positions of the scraper blades and of the stop screws and blade clamp have been illustrated in dot-and-dash lines in Figs. 2 and 7.

It should be noted that the foregoing scraper mount lends itself to such adjustment due to the fact that the scraper is free floating; that is to say, the scraper has an unrestrained vertical movement within the range of shifting of the rollers 64 in the slots 66, 6a." This ran e descent of the-intermediate plate 58 with respect to the outer plate 56.

For certain types of stencils and certain types of inks, the weight of the scraper and its mount may be too great, a in for example, too much ink to be expressed through the stencil. In order .that this may be regulated, means is provided to resiliently carry a'selectively variable part of the weight of the scraper and its mount. Said means includes a vertical post 158 whose base is secured to the stud 6%. The post is threaded at its upper end to receive an adjusting nut 160 and a lock nut 162, each of which is providedwith a handle to facilitate its manipulation.

Seated on the upper edge of the outer plate 56 is a bracket 164 having an outwardly extending horizontal flange 166 which is apertured to pass the post 158. A compression spring 168 encircles the post and is located between the adjusting nut 160 and the flange 166, said flange and nut being provided with wells to maintain the spring 168 in position. To relieve the stencil from the full weight of the scraper and its mount, the adjusting nut 160 is screwed downwardly. This has the effect of tending, to raise the intermediate plate and therefore the. scraper and its mount, spring 168 so i the support for the-raising action being the that said support is resilient.

The scraper can be arranged to operate' with a single blade simply by substituting a different form of clamp 17% (see Figs. 10 and 11) for the clamps 142. The clamp 174 includes a through slot 172 in which the pin 140 is received. Said clamp also has an abutment lug 152 de signed to oscillate between the two adjustable stop screws 154, 156. The clamps support a single scraper blade 174 which is allowed to oscillate as much as is desired by movement of the lug 152' between the two stop screws, it being understood that the blade does not oscillate during a stroke but only upon reversal; that is to say, the blade will lean forward in the direction in which it is traveling the extent of its inclination being determined by the positions of the stop screws. Such inclination and reversal at the two ends of the stroke is facilitated by the slots 172 and by offsetting the center of gravity of the blades relative to the pins 140, although it is within the scope of my invention to eliminate such ofiset.

When using the scraper with a single-blade, it is unnecessary and undesirable for the arm 82 to rock at opposite ends of the scraper stroke, and to prevent this from occurring said arm is provided with a lock pin 176, having a non-circular portion 178 of its shank disposed in a radial slot 183 in the arm 82. Said pin extends outwardly as far as the intermediate plate 58, and the bottomedges of the innerplate and intermediate plate are form-ed with notches 182, 184, respectively, which are adapted to receive the tip of said locking pin.-

When the two-blade clamp 142 is employed, the locking pin is disposed at the lower end of the slot 180 where its tip will clear the inner and intermediate plates. When the single-blade clamp is used, the arm 82 is forced to a vertical position (with the spindle 130 on top of the hump of the W-shaped notch 134) and the pin 17% raised and tightened in such position. Movement of the arm 82 to vertical position shifts the inner plate in respect to the intermediate plate and thereby aligns the two notches 152, 184 so that they are able to receive the lock pin when the same is raised. In addition, when the singleblade clamp 170 is used, the follower 90 is removed from the machine as indicated in Figs. 10 and 11. Thus, when the scraper approaches an end of the machine, the cam section a-b will be engaged by the follower 106 to raise the scraper and permit the blade 174 to clear the pool of ink I so that when the scraper moves in the opposite sweetene directioniit will-dro' i down with it's free 'edgeibehindsaid pool; It will-be observed'that-theinertiaofthe pendant-f scraper hlade will sufiice to change its inclination and therefore descend -on the proper" side' of the pool of "ink; this-:beingassiste'd by-the offset position of-the center of gravitysof 'the scraper;

It thus will be seen 'thatthere' is provideda device in: a which the several objects of this invention are achieved,

and whichis welhadapted to-meettli'e conditions'of practical use.

As various possible'embbdimentscmight,bc made of the above invention, and as variohs changes 'might be made in the embodiment ab'ove set forth, it is to be understood that all matter herein described OIShOWnaiIldhE accompanying drawings; is -tobe 'interpretedas illustrative and not in -a-:limiting 'sense.- a t Havingathus-de'scribed theinve'ntion, there is claimed asnewanddesired tobe secured by Letters Patent:

l. In-a siik screen printing rnachine having-ascraper lift thetsa'me vertically whereby the ba rwill be raisedas itapproachessaid end 'of the machine, meansatan end of the machine to engage the seondmamedmemberand shift-the sa-me' horizontally with respect to the first member-'as said members reach said end-of the machine; andmeansoper'able upon such 'horizontal shifting of the second-named'member-"to move th'e bar from one extreme angular position to -another.

2. A "co'mbination as set forth in claim l, wherein the last-named means ineludes arr-arm oscillatable with the ban-a horizontal spindle carriedby said arm, each memher having 'a'not'ch, the notch' in the first-named member having-two' indentations 'in its bottom edge, said spindle beings-located in one indentation of the notch in thefir'st nam'ed m'emherand in the other notch so that when th'e second-namedmember shifts horizontally with respect' 'to the first-named member, the spindle will be moved' from one indentationto the other of the notch in the first-named member, thereby oscillating the bar 3; A combination-as set forth inclaiin'2, wherein the spindle is mounted on a block 'slidable' in the arm and wherein a' spring biases theblock into engagement with the' 'indentatio'ns:

4. In afsilkscieen "printing machine havingla scraper carrying bar; m'e'ansto-support the ends of the bar, said means comprising a'truck at'each end of 'the bar, each trlick' including an outei plate, an intermediate plate and an'-'inner plate means to fix s'aid outer'plate'to said truck, means to' mount said intermediate plate on said outer plate for relative vertical movement, means to mount said inner plate on said intermediate plate for relative honientalz nieveniehe means -eseiuatably'suppen said bar from said intermediate 'plate; os'cillatable 'with said bar an: ar'rni'a blhcl; mansto slidably 'mountsaid "blobk in said=- ar'mfor mov s-raw toward --and' *away' from the? axis 'of oscillation"- of the biarj 'n'iaiis to resiliently urge" said block away rrem aia an' j odtivardly extehding spindle ca'i 'rie' b'y 'said ='bloek;' a w shaped' notch in said intermediate plate? a -V'-'shap'ed notchin' -sa'id outer plate',= said spindle bein'g' located saidnotches and resting ori thebas' of the w shaped notelf whereby wheh the inner plate is shiftd horiz'dntally*with resfiecttothe" intermediate -plate it will canse' the spindIe to" be moved) frem one side-ct th W slfalped notch "to" the other and mereby oscillate the" bar-a"vertica1-carri section on saidf inner plate; a a cam' follower at an fend of th'e'maclii e"*' for engaging" the" ca m section-"and shifting thein'n'er plate horizontally with= respect to th oute'r" plate' whe n th' truck reaches' said end-*0 machinejan inclined'c section on 'the' irln :1"-platej aeanrfollower engagingsai 0 second"ca'm sectioii' as*the' trucli' approacheshai'cl" end' off' the -machine"to raise the bar, a pair of hangers," means" to secure said hangers to said bar, ,a pair, offblade' clamps;' means-to moiiiit' a blade clamp" on each hanger "for relative iversrmovement-went aco'mmon"horizontal axis; means-*aa usebr 104mm the pivo-t'al movement of the blade clamps, a horizontal spindle, means to slidably mount *saidspindleErr-said arirrformovement toward and away near-hie aiiis of 'oscillatiomofthe'bar,"a pair of" notches 'in' th inner" and'outefplates; said notches being, in 'regi'stryfwliefi'"the spindle is disposed centrally in jthe" W-sliap'EdQtcIi; and means "to "lockthe'pin in anyse f lected position,infthe'arniwhereby; the pi'n'can be located to perniit the arm to"swing fi eely of canine disposedin the las t named pair of notches" to prevent relativ'e' hori-" zoiitalmoveinent' 'of e'in'ner and"intei'mediate plates;

5: A combination I asset forth "inc laim "4, wherein "a vertically extending compression spring has its lower end seated on 1h e""oute'rp1atefwherein a member is 'seated on'the uppe'r en'd'of the'compr'essio'n spring, and wherein" said membefis secured to" the" intermediate plate for vertical selectively adjustablemovenient;

6. In a silk" screen pri'ntingmachine having a scraper carrying .barja truck, means tdmounfanen'd' of- 'said' bar on saidtriick*forfreevertical movement, means to carry a selectively 'variable portion'of the wcight of the bar andscra'pef, saidfmeanscomprising .a vertically .eX- tending" compressiori spiing, "meaiis to seat thelow'er end of said "springonfl'sa'id trii c'k-ya member seated on the upper end ofjsaid'spring", and mean's' to secure said memher to an end of said barfor"vertical selectively' adjustable movement.

nferen scitd' in ihe'a e orf'thi's patent UNIT'Eo sT'ATEs PATENTS 

